DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] After performing various tests, the inventor discovered a way for an improved mounting for a semiconductor device using an insert-type package. The package includes a portion having thermal distortion-resistant characteristics to enable the package to be positioned relative to other members. That is, in the present invention, the support part has at least a first main surface disposed adjacent to the recess for housing the semiconductor element and a second main surface disposed adjacent to and offset from the first surface. The presence of at least two main surfaces enables the positioning of the package with respect to the other members.

[0049] The present invention will be described with reference to the accompanying drawings in which preferred embodiments of the invention are shown by way of example, especially by using the example of a light emitting device. FIGS. 1 - 5 show schematic perspective views and schematic cross sectional views of light emitting devices according to the present invention. In addition, FIGS. 16 A- 16 D show schematic cross sectional views of the molding process for the package of the present invention.

[0050] The light emitting device of the present invention has several embodiments. For example, as shown in FIG. 1A, a package 1 is formed by integral molding so that the end parts of both the positive and negative electrodes 2 can be inserted in the package 1 . A recess is formed on a first main surface la of the package 1 for housing the light emitting element 4 . The end portions of a positive electrode and a negative electrode are disposed on a bottom surface of the recess and are separated from each other while exposing their respective main surfaces. The gap between the positive and negative electrodes is filled with an insulating molding material.

[0051] Here, the term “main surface” in the present specification refers to a surface of the light emitting device which is on the same side as the side which emits light from the light emitting element. Furthermore, the configuration of the light emitting surface formed on the main surface of the light emitting device is not limited to a rectangular shape as shown in FIG. 1 A, but can be a elliptical shape as shown in FIG. 6 . With such a configuration, the light emitting surface area can be maximized while the mechanical strength of the side wall which forms the recess can be retained. This structure also enables the light emitting device to emit light into a wider area.

[0052] The positive electrode and the negative electrode of a light emitting device of the present invention are inserted so that they protrude from the side ends of the package. The protruding parts of the lead electrodes are bent rearwardly away from the main surface of the package, or they are bent toward the mounting surface perpendicular to the main surface. Here, the mounting surface is the surface that is perpendicular to the main surface of the package and that is parallel to the longer side of the recess. In this arrangement, the light emitting device of the present invention is a side light emitting type which emits light approximately parallel to the mounting surface.

[0053] The package 1 used in the present invention comprises a recess formed in the main surface and defined by an interior wall 8 of the package. A step can be formed by a side wall in the main surface of the package disposed away from the recess. More specifically, the side wall can be disposed between at least a first main surface 1 a which is adjacent to the recess and a second main surface 1 b which is a step lower than or set back from the first main surface 1 a. That is, a step is formed between the first main surface and the second main surface. This step is not necessarily provided perpendicularly to the longer sides of the first main surface. The step may be formed at an angle to the lengthwise direction of the semiconductor element as long as it facilitates fitting or matching of the semiconductor element device of the present invention relative to an external support part or an optical member. In addition, the shape of the step is not limited in shape to a single wall between the first main surface 1 a and the second main surface 1 b, as the step may also have more than two or three steps, which would then include a third main surface, a fourth main surface, etc. and several side walls between them. Because of this configuration, positioning of the device relative to other optical members, can be achieved uniformly by using at least the first main surface 1 a and the second main surface 1 b.

[0054] Attaching an optical member such as a lens having a specific shape to the device, or assembling a surface emitting light source by combining the light emitting device of present invention with an optical guide plate can be facilitated and enhances the light intensity and obtains the desired optical properties for the light emitting device in accordance with the present invention. At this time, by providing a shape on the optical member which is capable of fitting or matching with the shape of the main surface side having at least the first main surface 1 a and the second main surface 1 b of the light emitting device with no space between, a light source can be assembled with ease and precision. Therefore, a light source with excellent mass productivity and excellent optical properties can be obtained.

[0055] In addition, although the main surface has a step between the first main surface 1 a and the second main surface 1 b in the present embodiment, the present invention is not limited to a configuration having steps. It is also possible to have a main surface where the second main surface 1 b is continuous with the first main surface 1 a as shown in FIGS. 18A and 18B and described further below. By fabricating the mounting surface of the other optical members so as to fit the continuous first main surface la and second main surface 1 b with no space therebetween, the present invention provides a light emitting device having an excellent capacity for installation with other optical members.

[0056] According to the embodiment shown in FIG. 17A and 17B , the second main surfaces are defined by the protrusions 1 b on both ends of the support member 1 . The protrusions 1 b do not necessarily need to be formed at the ends of the support member. They may be formed at any location suitable for positioning of the semiconductor device.

[0057] The protrusions 1 b also do not necessarily need to perpendicularly extend to the longer side of the support member. They may also be formed as a groove extending diagonally with respect to the longer side, instead of a protrusion, as shown in FIGS. 21A and 21B .

[0058] Additionally, as shown in FIGS. 18A and 18B , the first main surface and the second main surface are continuous and angularly offset from each other. There is a dividing line between the first main surface and the second main surface on each side of the recess. The two dividing lines on the package that separate the second main surfaces from the first main surfaces do not necessarily need to be straight lines. These dividing lines (or surface interfaces) could also be curved. Similarly, the dividing surface separating the first main surface and the second main surface in the embodiments when they are offset, do not necessarily need to be planar. These surfaces can also be curved surfaces.

[0059] FIGS. 19A and 19B and FIGS. 20A and 20B show embodiments where the second main surface can be formed as a circular recess or a protrusion, respectively. The recess or protrusion does not necessarily need to be a circular. They also may other shapes including polygonal shapes.

[0060] Furthermore the recess and the protrusion may be shaped as a circular groove as shown in FIGS. 22 A and FIGS. 22B or as a raised circular wall as shown in FIGS. 23A and 23B . It is also possible to use differently shaped grooves, walls and/or recesses.

[0061] FIGS. 24A and 24B show an embodiment where the second main surface includes a protrusion such as a circular or elliptical protrusion.

[0062] FIGS. 25A and 25B show an embodiment where the second main surface includes a recess such as a circular or elliptical recess.

[0063] FIGS. 26A and 26B show an embodiment where the second main surface includes a protrusion which is formed so as to angularly extend between the opposed sides of the package.

[0064] As seen in the embodiments described above, the configuration defined by the first main surface and the second main surface of the present invention can be designed considering the position of the semiconductor, the viscosity of the adhesive as well as other factors.

[0065] FIGS. 16A through 16D show schematic cross sectional views showing the molding process of the package 1 according to one embodiment of the invention. The molding process of the package of the present invention is described in steps (a) through (d) below. (a) First, a lead frame 24 formed by punching a metal plate is sandwiched between the die 27 having a protrusion and the die 28 having a cavity. The lead frames 24 are placed in the resin-sealing space formed by the die 27 having a protrusion. The die 28 has a cavity so that the tip portions of the lead frames 24 are arranged so as to be opposite from each other and are spaced apart by a predetermined interval. (b) Next, as shown with the injection direction 29 of package molding member 26 , the package molding member 26 is injected into the through-hole formed in the direction of the resin-sealing space, and the resin-sealing space is filled with the package molding member 26 . (c) The package molding member 26 is then heated to cure the resin. (d) First, the die 28 having the cavity is removed and the pushing member 25 is shifted in a thrust direction 30 toward the second main surface 1 b, which is a pin-knock face. Then the package 1 can be removed from the die 27 having a protrusion.

[0066] As described above, the package 1 formed by injection molding used in a light emitting device according to the present invention, is first formed in a mold. Then the package 1 is detached from the mold by pushing it out with a pushing member 25 , such as a pin or the like, equipped in the mold.

[0067] However, when detaching the package, the molding member of the package still remains hot and is susceptible to deformation by external forces. For example, in the case wherein a main surface of the lead electrode 2 in the recess is used as a pin-knock surface, weak mechanical strength of the molding member may cause dislocation or deformation of the lead electrode 2 . This can result in mounting the light emitting element 4 on a tilt, and thus the light emitting devices may not all be oriented for emitting light in the same direction. Therefore, it is necessary to arrange a pin-knock surface on the surface of the package 1 .

[0068] In the case where the light emitting device is downsized, the end part of the package must be arranged as the pin-knock surface. However, it is possible that the package 1 may still be soft when detaching it from the molding die. If so, a part of the molding material may be pushed inwardly when knocked by the pin. In the case where the pin-knock surface is provided on the upper surface of the first main surface adjacent to the recess, the mold material that was pushed back may shift toward the light reflecting surface. This process causes deformation of the light reflecting surface and this may exert a damaging effect on the optical properties of the light emitting device.

[0069] In contrast, the light emitting device according to the present invention has the first main surface 1 a and the second main surface 1 b disposed in sequence outwardly from the recess which includes the light emitting surface. Therefore, the package can be detached from the die by arranging the second main surface as the pin-knock surface. This prevents deformation of the recess and enables mass production without causing a damaging effect to the light emitting properties.

[0070] The configuration of the second main surface 1 b according to the present invention is not specifically limited. It is preferable to have a elevated portion 1 c on the second main surface 1 b, and it is also preferable to set the height of the elevated portion 1 c to be lower than the height of the first main surface. According to this configuration, the contact area between the second main surface 1 b and the adhesive member or the like, can be increased when fixing the light emitting device according to the present invention to other members, thereby enhancing their adhesion strength. Furthermore, as shown in FIGS. 2 - 4 , it is preferable to form the external wall of the elevated portion 1 c so that it is surrounding a depression. When the depression is filled with an adhesive member and it is fixed to an optical member or the like, the external wall prevents the adhesive member from flowing toward the lead electrode or the first main surface 1 a. This forms a light emitting device with excellent reliability and excellent optical properties. In addition, the configuration having a protrusion 1 c on the second main surface 1 b can also be formed at the same time using process step (d) for removing the package 1 , by pressing the pushing member 25 against the second main surface 1 b.

[0071] The package 1 of an embodiment of the present invention has a recess capable of housing the light emitting element 4 . The shape of the inner wall of the recess is not specifically limited. In the case where the light emitting element 4 is mounted, it is preferable to make the inner wall as a tapered wall, where its internal diameter widens toward the opening. This arrangement enables light emitted from the end face of the light emitting element 4 to pass through the light observation surface. In addition, a light reflection function can be added so as to enhance the light reflectivity, by providing a metal plating with Ag or the like on the inner surface of the recess.

[0072] In the light emitting device according to this embodiment of the present invention, the light emitting element 4 is placed in the recess of the package 1 formed as described above. Then a translucent resin is filled in the recess so as to cover the light emitting element 4 with a sealing portion 3 .

[0073] In the following description, the production process and the individual components of the embodiments of the present invention will be described in more detail.

[0074] Process 1: Formation of the Lead Electrodes

[0075] In the present embodiment, the first process includes pulling a metal sheet to form a lead frame having plurality of pairs of positive and negative lead electrodes. Next, a plating operation is performed on the surface of the lead frame. In addition, a hanger lead which supports the packages throughout the production processes, from the step of lead electrode formation through the step of light emitting device partition, can be provided on a portion of the lead frame.

[0076] Lead Electrodes 2

[0077] The lead electrodes 2 in the present embodiment are electric conductors which supply power to the light emitting element and are capable of having the light emitting element mounted thereon. Particularly, the lead electrodes 2 are formed by integral molding so that one end of the lead electrode is inserted into the package and the other end protrudes from a surface of the package. In addition, the main surfaces of the end portions of the inserted electrodes 2 are exposed on the bottom surface of the recess in the package.

[0078] Although the materials for the lead electrodes 2 are not specifically limited except for related to conductivity, good adhesiveness with conductive wires 5 which form electrical connections with the semiconductor element and conductive bumps 6 as well as good electric conductivity are required. As an example of the value of the electrical resistance, 300 μΩ-cm or less is preferable and 3 μΩ-cm or less is more preferable. As for the material fulfilling such conditions, iron, copper, copper containing iron, copper containing tin, and aluminum, iron, or copper plated with gold or silver are preferably used.

[0079] In each portion of the pressed metal long sheet corresponding to a part of the package, an end face of the positive electrode is disposed so as to be separated from the negative electrode and opposite from an end face of the negative electrode. In the present embodiment, a specific process is not carried out on the lead electrode 2 where their surfaces of the end portions are exposed in the bottom face of the recess. However, the bond strength with the molding resin can be enhanced by providing at least a pair of through-holes on either side of the axis in the longitudinal direction of the recess.

[0080] Process 2: Formation of the Package

[0081] In the present embodiment, a package 1 is capable of mounting a light emitting element 4 . The package 1 functions as a support member for securing the lead electrodes 2 where the light emitting element 4 is mounted. The package 1 also protects the light emitting element 4 and the conductive wires 5 from the external environment.

[0082] Next, the metal long sheet described above is placed between the mold 28 having a recess and the mold 27 having a protrusion and then the molds are closed. The molding member is injected into the cavity created by the closed molds, through a gate provided at the back face of the mold having a recess. The cavity described above corresponds to the outer shape of the package. In the present embodiment, the molds for shaping the molding resin portion are provided with steps on the main surface of the package. This structure obtains a package 1 having the first main surface 1 a and the second main surface 1 b which is placed a step lower than the first main surface 1 a, and is also further from the recess than the first main surface 1 a. In addition, it is preferable to insert the pressed metal long sheet between the mold 28 having a recess and the mold 27 having a protrusion in such way so that the direction of punching coincides with that of injection of resin into the molds. According to such placement of the metal long sheet, the resin can be filled in the space formed by the end portions of the positive and negative electrodes without leaving gaps. This arrangement also prevents molding resin from flowing out onto either of the main surfaces.

[0083] Furthermore, in the case where a hanger lead is provided on the lead frame, as shown in FIG. 3 A, package 1 is formed having a recess on its side face corresponding to the shape of the end portion of the hanger lead. The hanger lead can also support the package throughout the production processes.

[0084] Molding Material

[0085] The molding material for the package used in the present invention is not specifically limited. A liquid crystal polymer, a polyphthalamide resin, a polybutylene terephthalate (PBT), or the like, as well as any other known thermoplastic resins can be used. When a semi-crystalline polymer resin containing crystals of high-melting point is used such as polyphthalamide resin, a package having a large surface energy and good adhesion with a sealing resin in the recess or with an optical guide plate, can be obtained. Accordingly, interfacial separation between the package recess and the sealing resin can be prevented when they are cooled. In addition, a white pigment substance such as titanium oxide or the like, can be mixed into the molding member of a package to enhance the efficiency of the reflection of light emitted from the light emitting chip.

[0086] The molding member formed in such a manner is detached from the mold as follows. First, the mold is opened, and the pin provided in the mold having a protrusion is thrust toward the second main surface of the package. At this moment, a cylindrical wall having an inner diameter which is the same as the size of a pinhead is formed. Such a cylindrical wall can prevent the flow of adhesive material while fixing the light emitting device to other members by using an adhesive material or the like, and can achieve an enhanced adhesive force.

[0087] Process 3: Mounting of the Semiconductor Element

[0088] Next, the semiconductor element is fixed to the lead electrode 2 exposed in the bottom face of the recess formed in the package 1 . In the present embodiment, a semiconductor element will be illustrated as an example of a light emitting element. However, the semiconductor element used in the present invention is not limited to this light emitting element, and can be a photodetector, an electrostatic protection element (Zener diode), or an element which is made by a combination of at least two of these elements.

[0089] Light Emitting Element 4

[0090] As an example of the semiconductor element in the present invention, a semiconductor element may be used such as a light emitting element, a light receiving element, or the like. The semiconductor element in the present embodiment can also be an LED chip used as a light emitting element.

[0091] The light emitting element 4 is not specifically limited in the present invention. In the case where a fluorescent material is concurrently used, it is preferable to use a semiconductor light emitting element having an active layer capable of emitting light with a wavelength capable of exciting the fluorescent material. As an example of such a semiconductor light emitting element, various semiconductors such as ZnSe or GaN can be used. However, a nitride semiconductor (In _x Al _y Ga _1−x−y N, 0≦X, 0≦Y, X+Y≦1) capable of emitting light with a short-wavelength that can sufficiently excite the fluorescent material is preferable. The nitride semiconductor may contain boron or phosphorus if needed.

[0092] As an example of the structure of the semiconductor, a homostructure, a heterostructure or a double heterostructure having an MIS junction, a PIN junction or a P-N junction can be used. A variety of emission light wavelengths can be selected depending on the materials or the degree of the mixed crystal in the semiconductor layers. In addition, the active layer can be of a single well structure or a multiple well structure, formed as a thin film wherein a quantum effect occurs.

[0093] In the case where a nitride semiconductor is used, a material such as sapphire, spinel, SiC, Si, ZnO, GaN, or the like, is preferably used as the semiconductor substrate. It is preferable to use a sapphire substrate in order to form a nitride semiconductor having good crystallinity and which can be efficiently produced in quantity. A nitride semiconductor can be formed on the sapphire substrate in accordance with MOCVD or the like. For example, a buffer layer, such as of GaN, AlN, GaAlN, or the like, can be formed on a sapphire substrate, and a nitride semiconductor having a P-N junction can be formed thereon. Furthermore, the substrate can be removed after formation of the semiconductor layers.

[0094] An example of a light emitting element having a P-N junction using a nitride semiconductor includes, for example, a double heterostructure wherein a first contact layer of N-type gallium nitride, a first cladding layer of N-type aluminum gallium nitride, an active layer of indium gallium nitride, a second cladding layer of P-type aluminum gallium nitride, and a second contact layer of P-type gallium nitride, are layered on the buffer layer in sequence. Nitride semiconductors show N-type conductivity when in the condition where no impurities have been doped. In order to form an N-type nitride semiconductor having the desired properties such as improved light emission efficiency, it is preferable to arbitrarily introduce an N-type dopant such as Si, Ge, Se, Te, C, or the like. On the other hand, in order to form a P-type nitride semiconductor, it is preferable to dope with a P-type dopant such as Zn, Mg, Be, Ca, Sr, Ba, or the like.

[0095] Due to the fact that a nitride semiconductor is not easily converted to the P-type solely by doping a P-type dopant, it is preferable to treat such a semiconductor after introduction of the dopant in processes such as heating in a furnace or irradiation with plasma. After forming the electrodes, the semiconductor wafer is cut into chips so that the light emitting elements of the nitride semiconductor can be obtained. In addition, an insulating protective film made of materials such as SiO ₂ can be made by means of patterning and which covers the entire element except the bonding parts of each electrode which are exposed. Thus with this arrangement, downsized light emitting devices can be obtained with a high reliability.

[0096] In order to emit white light by using the light emitting diode of the present invention, it is preferable for the wavelength of light emitted from the light emitting element to be greater than or equal to 400 nm and less than or equal to 530 nm, and more preferably greater than or equal to 420 nm and less than or equal to 490 nm. These ranges take into consideration the complementary color relationship with fluorescent material and deterioration of the translucent resin, or the like. Furthermore, it is more preferable for the wavelength to be greater than or equal to 450 nm and less than or equal to 475 nm, in order to improve the excitation and the emission efficiency of the light emitting element and the fluorescent material. In addition, the light emitting elements having a main emission wavelength less than 400 nm, which is in ultraviolet region, or the short wavelength range of visible light can be used in combination with members relatively resistant to deterioration by ultraviolet light.

[0097] Bump 6

[0098] The light emitting element 4 in the present embodiment can obtain uniform emission when mounted by the flip tip method because there is no obstacle to shield emission at the light emitting face side. This method includes a pair of electrodes or bumps 6 provided on the same face side and placed to face a pair of lead electrodes exposed in the recess of the package. The material for the bumps 6 is not specifically limited except for its conductivity. It is preferable for the bumps 6 to contain at least one material which is included in the positive and negative electrodes of light emitting element or in the plating material of the positive and negative lead electrodes. In the present embodiment, a bump of Au is formed on each lead electrode 2 , and each bump 6 and each lead electrode 2 are placed so as to be opposed to each other. Then these elements are bonded by ultrasonic soldering.

[0099] As an example of a different bump forming process, a stud bump can be obtained by cutting the wire so as to leave the edge portion of the wire after bonding an edge portion of the conductive wire. In another process, a bump can be obtained by metal deposition after forming the desired mask pattern, or the like. In addition, a bump can be provided first to the electrode side of the light emitting element, or it can be provided to both the lead electrode side and the light emitting element side, respectively.

[0100] In addition, it is preferable to mount through a sub-mount when mounting by the flip tip method. FIG. 7 shows a schematic perspective view of mounting the light emitting diode 4 via a sub-mount according to an embodiment of the present invention. In the flip tip method, the interface between the light emitting element and the lead electrode 2 connected through the bump 6 is susceptible to separation caused by slippage of the lead electrode 2 due to thermal stress. In addition, it is difficult to narrow the space between opposed end portions of the positive and negative lead electrodes similar to the space between the positive and negative electrodes of the light emitting element. Therefore, it is difficult to achieve a stable connection of the light emitting element to lead electrode. By choosing the most suitable package materials, most of these problems can be solved to some degree, however, further improvement in the reliability of the light emitting device can be achieved with ease by using a flip tip mounting process via a sub-mount.

[0101] A conductive pattern provided by a conductive member 12 is placed on the surface of a sub-mount substrate 11 so as to extend from the side facing the light emitting element 4 to the side facing the lead electrode 2 . The space between each of the conductive patterns can be as narrow as the space between the positive and the negative electrodes of the light emitting element 4 by using an etching method. The material for the sub-mount substrate 11 preferably has a thermal expansion coefficient approximately the same as that of the light emitting element 4 , such as aluminum nitride in a nitride semiconductor element. The effect of thermal stress existing between the sub-mount 11 and the light emitting element 4 can be reduced by using such a material. Alternatively, silicon, which is capable of serving as an electrostatic protection element and is moderate in price, is preferred as the material for the sub-mount substrate 11 . In addition, silver or gold having a high reflectivity is preferable for the conductive member 12 . Further, it is preferable to provide holes in or concave or convex patterns on the surface of the sub-mount substrate except in the portion which would negatively affect mounting of the light emitting element 4 . This configuration allows heat generated by the light emitting element 4 to be released effectively from the sub-mount. It is preferable to form more than one of the through-holes in the sub-mount substrate 11 in the direction of the thickness of the sub-mount substrate, and extend the above-described conductive member 12 to the inner wall of the through-hole, so that heat release can be increased further. In addition, the sub-mount in the present embodiment is directly connected to the conductive pattern and the lead electrode, and thus the conductive pattern may be connected to the lead electrode via a conductive wire.

[0102] In order to improve the reliability of the light emitting device, an underfill can be used between the positive and negative electrode of the light emitting element and the sub-mount. An underfill can also be used in the gap existing between the positive and negative electrodes of the light emitting element and the lead electrodes 2 exposed in the bottom of the recess of the package.

[0103] A thermosetting resin such as an epoxy resin may be used as a material for the underfill. In order to reduce thermal stress in the underfill, aluminum nitride, aluminum oxide, and their composite mixtures can be mixed into the epoxy resin. The amount of underfill required is an amount sufficient to fill the gap that occurs between the positive and negative electrodes of the light emitting element and the sub-mount.

[0104] The connection between the conductive pattern formed on the sub-mount and the electrode of the light emitting element 4 is made using an ultrasonic bonding method that includes a cementing material such as Au, an eutectic solder (Au—Sn, Pb—Sn), a lead-free solder or the like. Also, the connection between the conductive pattern formed on the sub-mount and the lead electrode can be made using a cementing material 10 such as a Au paste, a Ag paste or the like.

[0105] Conductive wires 5

[0106] After using die bonding to fix the light emitting element 4 onto one of the lead electrodes, each of the electrodes of the light emitting element can be connected by the conductive wires 5 . Here, the cementing material used in die bonding is not specifically limited and insulating adhesives such as epoxy resin, Au—Sn alloy, resin or glass containing conductive material, or the like, can be used. It is preferable to use Ag as the conductive material. A light emitting device having excellent heat radiation and having a low stress after cementing can be obtained by employing Ag paste with 80% to 90% Ag content.

[0107] For the conductive wires 5 , excellent properties for Ohmic contact, mechanical connectivity as well as electric and thermal conductivity are required. For thermal conductivity, 0.01 cal/(s)(cm2)(° C./cm) or greater is preferable, and 0.5 cal/(s)(cm2)(° C./cm) or greater is more preferable. In addition, it is preferable that the diameter of the conductive wires be greater than or equal to 10 μm and less than or equal to 45 μm in view of efficiency.

[0108] The conductive wire is susceptible to separation at the interface of the coating portion, which includes the fluorescent material, and the molding member, which does not include the fluorescent material. Even when the same material is used for both the coating portion and the molding portion, the fluorescent material is believed to be the cause of the separation due to a difference in thermal expansion. For this reason, the diameter of the conductive wire is preferably greater than or equal to 25 μm. For the reasons of enlarging the light emitting area and ease of handling, the diameter of the conductive wire is preferably less than or equal to 35 μm. The conductive wire can be a wire made of a metal such as gold, copper, platinum, aluminum, or the like, or an alloy using these metals.

[0109] Process 4: Sealing

[0110] Next, a sealing member 3 is provided to protect the light emitting element 4 from the external environment. The sealing step is carried out by filling the recess of the package 1 with the sealing member 3 so as to cover the light emitting element 4 and the conductive wires 5 . Once the sealing member 3 fills the recess, the sealing member 3 begins to harden.

[0111] Sealing member 3

[0112] The properties material of the sealing member 3 are not specifically limited except for having translucency. A translucent resin having excellent properties for withstanding the weather, such as silicon resin, epoxy resin, urea resin, fluorocarbon resin, or a hybrid resin containing at least one of the resins, or the like, can be used as the sealing member 3 . In addition, the sealing member 3 is not limited to an organic material. An inorganic material having excellent light resistance such as glass or silica gel can also be used. In addition, a sealing member can be made from many other materials, such as a thickening agent, a light diffusion agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, silicon dioxide, calcium bicarbonate, calcium carbonate, or a mixture including at least one of these materials.

[0113] Furthermore, the sealing member can obtain a lens property by making the emission face side of the sealing member into a desired form. The sealing member 3 functions to focus the light emitted by the light emitting chip. In addition, in the case where a semiconductor element is used as a light receiving element, the sensitivity of the light receiving device can be enhanced by arranging the sealing member so that light is guided and condensed in the direction of the light receiving element. For instance, the sealing member may be shaped as a convex lens or a concave lens. Further, the sealing member may also have an elliptic shape or some combination of these shapes.

[0114] Fluorescent material

[0115] In the present invention where a semiconductor element is used as the light emitting element, a variety of fluorescent materials made of inorganic materials or organic materials can be employed. These materials can be used in or around each of the components, such as the light emitting element, the sealing member, the die bonding member, the underfilling, or the package. For example, the fluorescent material can include a rare earth element which is an inorganic fluorescent material.

[0116] For the fluorescent material having a rare earth element, a garnet type fluorescent material including at least one element selected from the group comprising Y, Lu, Sc, La, Gd, Tb and Sm, and at least one element selected from the group comprising Al, Ga and In can be used. Specifically, the aluminum-garnet phosphor used in the present embodiment can be a phosphor that contains Al and at least one element selected from Y, Lu, Sc, La, Gd, Tb, Eu, Ga, In, and Sm, and that is activated with at least one element selected from the rare earth elements. The phosphor is excited by the visible light or ultraviolet rays emitted from the light emitting element and therefore the phosphor emits light. For example, in addition to the yttrium-aluminum oxide phosphor (YAG phosphor) described below, Tb _2.95 Ce _0.05 Al ₅ O ₁₂ , Y _2.90 Ce _0.05 Tb _0.05 Al ₅ O ₁₂ , Y _2.94 Ce _0.05 Pr _0.01 Al ₅ O ₁₂ , Y _2.90 Ce _0.05 Pr _0.05 Al ₅ O ₁₂ , or the like, can be used. Among them, more than two kinds of yttrium-aluminum phosphors of different compositions, each containing Y and activated with Ce or Pr can be used.

[0117] In addition, the nitride phosphor used in the present invention is a phosphor that contains N, at least one element selected from Be, Mg, Ca, Sr, Ba and Zn, and at least one element selected from C, Si, Ge, Sn, Ti, Zr and Hf, and activated with at least one element selected from the rare earth elements. Furthermore, the nitride phosphor used in the present embodiment is a phosphor that absorbs visible light or ultraviolet rays emitted from the light emitting element or YAG phosphor and this causes a light emission from the phosphor. Examples of nitride phosphors, include (Sr _0.97 Eu _0.03 ) ₂ Si ₅ N ₈ , (Ca _0.985 Eu _0.015 ) ₂ Si ₅ N ₈ , (Sr _0.679 Ca _0.291 Eu _0.03 ) ₂ Si ₅ N ₈ , or the like.

[0118] Each of the phosphors will be described in detail below.

[0119] Yttrium-Aluminum Oxide Phosphor

[0120] The fluorescent material used for the light emitting device in the present embodiment uses a yttrium aluminum oxide phosphor activated with cerium which is excited by the light emitted from the semiconductor light emitting element having an active layer, and which is capable of emitting light in different wavelengths. Specifically, YAlO ₃ :Ce, Y ₃ A ₁₅ O ₁₂ :Ce(YAG:Ce) or Y ₄ A ₁₂ O ₉ :Ce, as well as a mixture of these compounds can be used as yttrium aluminum oxide phosphors. At least one element of Ba, Sr, Mg, Ca and Zn can be contained in the yttrium aluminum oxide phosphor. In addition, the particle size of the fluorescent material can be controlled by adding Si in order to restrain the crystal growth reaction. In the present specification, the yttrium aluminum oxide phosphor activated by Ce should be broadly interpreted as including fluorescent materials having a fluorescent property with part or all of the yttrium substituted with one of the elements selected from the group comprising Lu, Sc, La, Gs and Sm, or with a portion or all of aluminum substituted with one or two elements of Ba, Tl, Ga and In.

[0121] In further detail, the fluorescent material is a photoluminescence fluorescent material represented by the general formula (Y _z Gd _1−z ) ₃ Al ₅ O ₁₂ :Ce (wherein 0<z≦1), or a photoluminescence fluorescent material represented by the general formula (Re _1−a Sm _a ) ₃ Re′ ₅ O ₁₂ :Ce (wherein 0≦a<1, 0≦b≦1, Re is at least one element selected from Y, Gd, La and Sc, and Re′ is at least one element selected from Al, Ga, and In). The above described fluorescent material has a garnet structure, and therefore it has properties resistant to heat, light and moisture, and is capable of being adjusted so that its peak wavelength of its excitation spectrum is about 450 nm. In addition, the fluorescent material emits light having a peak emission wavelength of about 580 nm and a broad emission spectrum which gradually diminishes toward the 700 nm range.

[0122] The excitation luminous efficiency in the long-wavelength range of 460 nm and above can be improved by including Gd in the crystal of the photoluminescence fluorescent material. By increasing in the content of Gd, the peak emission wavelength shifts toward a longer wavelength, and the wavelength of the entire emission spectrum also shifts toward longer wavelengths. That is, when emission of a more reddish light is required, it can be obtained by increasing the degree of substitution of Gd. On the other hand, when the Gd content is increased, the light of photoluminescence in terms of blue light tends to decrease. Tb, Cu, Ag, Au, Fe, Cr, Nd, Dy, Co, Ni, Ti, Eu, Pr, or the like can be included in addition to Ce if desired.

[0123] In addition, by substituting a part of Al with Ga in the composition of yttrium aluminum garnet fluorescent material, the emission wavelength can be shifted toward a shorter wavelength. On the other hand, by substituting a part of Y with Gd, the emission wavelength can be shifted toward a longer wavelength. When substituting a part of Y with Gd, it is preferable to limit the substituted Gd to less than 10%, while adjusting the degree of substitution of Ce from 0.03 to 1.0 in the molar ratio. When substituted Gd content is less than 20%, the green component in the emission is greater and that of the red component is less. However, by increasing the content of Ce, the red component in the emission can be compensated, and a desired color tone can be obtained without decreasing the luminance. According to such a configuration, desirable temperature characteristics of the fluorescent material can be obtained, thereby improving the reliability of the light emitting diode. Also, when the photoluminescence fluorescent material that is adjusted to include a more reddish component is used, a compound color such as pink can be emitted, thereby enabling the light emitting device to be formed with excellent color rendering properties.

[0124] The raw material for making such a photoluminescence fluorescent material is made in such a way that sufficiently mixes oxides of Y, Ga, Gd, Al, and Ce or compounds which can be easily converted into these oxides at high temperature as raw materials for Y, Ga, Gd, Al, and Ce in accordance with the stoichiometric ratio. The mixture material may also be made by dissolving rare earth elements Y, Gd, and Ce in stoichiometric proportions in an acid, coprecipitating the solution with oxalic acid and firing the coprecipitation to obtain an oxide of the coprecipitate, and then mixing it with aluminum oxide.

[0125] The obtained raw material is mixed with an appropriate amount of fluoride, such as barium fluoride or ammonium fluoride used as a flux, and is charged into a crucible and fired at 1350-1450° C. in air for 2 to 5 hours to obtain the calcinated material. The calcinated material is then ball-milled in water, washed, separated, dried, and finally, sieved thereby obtaining the desired material.

[0126] Also, the firing above is preferably carried out in two steps. The first step includes firing the mixture of raw materials for the fluorescent material and the flux in air or in a slightly reduced atmosphere. The second step includes firing them in a reduced atmosphere. The slightly reduced atmosphere means an atmosphere containing at least the necessary amount of oxygen for the reaction process to form a desired fluorescent material from the mixed raw materials. By carrying out the first firing step in the slightly reduced atmosphere until the formation of the desired structure for the fluorescent material has completed, darkening of the fluorescent material and deterioration in its light absorbing efficiency can be prevented.

[0127] Also, the reduced atmosphere in the second firing step means an reduced atmosphere stronger in the degree of reduction than the above discussed slightly reduced atmosphere. Therefore, a light emitting device employing a fluorescent material produced as described above can achieve a reduction in the quantity of phosphor necessary to obtain light with a desired color tone. It is also possible to obtain a light emitting device having an excellent light extraction efficiency.

[0128] Silicon Nitride Fluorescent Material

[0129] Also, a fluorescent material which is excited by absorbing light such as visible light emitted from the light emitting element, ultraviolet or light emitted from other fluorescent materials to thereby emit light, can be used. Specifically, a silicon nitride fluorescent material in which Mn is added, such as Sr—Ca—Si—N:Eu, Ca—Si—N:Eu, Sr—Si—N:Eu, Sr—Ca—Si—O—N:Eu, Ca—SiO—N:Eu, and Sr—Si—O—N:Eu, as component elements can be used. The fluorescent materials described above are represented by general formulas L _X Si _Y N _(2X/3+4Y/3) :Eu or L _X Si _Y O _Z N _{(2X/3+4Y/3−2Z/3)} :Eu (wherein L is one of Sr, Ca, Sr, or Ca). In the general formula, X=2, Y=5, or X=1, Y=7 is preferable, although arbitrary numbers can also be applied.

[0130] More specifically, it is preferable to use a fluorescent material in which Mn is added and represented by the general formulas (Sr _X Ca _1−X ) ₂ Si ₅ N ₆ :Eu, Sr ₂ Si ₅ N ₈ :Eu, Ca ₂ Si ₅ N ₈ :Eu, Sr _X Ca _1−X Si ₇ N ₁₀ :Eu, SrSi ₇ N ₁₀ :Eu, or CaSi ₇ N ₁₀ :Eu. However, the fluorescent material can also include at least one element selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, and Ni. The proportion of Sr and Ca can also be changed when desired. Further, a fluorescent material having excellent crystallinity can be provided at a low price by including Si in the formula.

[0131] When Eu ²⁺ is used as an activator for the host crystal of silicon nitride with alkaline-earth metals, it is preferable to use a material wherein O is removed from Eu ₂ O ₃ , such as elemental Eu or europium nitride. However, this is not limited to the case where Mn is added. Adding Mn accelerates the diffusion of Eu2+, and thereby improves the luminous efficiency such as luminance, energy efficiency and quantum efficiency. Mn is included in a raw material, or it is included during the production process as an element or a compound. Then it is fired with the raw materials. However, after firing, Mn is not included among the basic component elements, or remains small in proportion to its initial content. This is considered to be due to the scatter of Mn in the firing process.

[0132] Also, by including at least one element selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, O, and Ni, a fluorescent material can easily be obtained in a large particle size with an improved luminance. Also, B, Al, Mg, Cr, and Ni have properties that can restrain afterglow.

[0133] The nitride fluorescent material described above absorbs a portion of blue light and emits light from the yellow region to the red region. A combination of such a nitride fluorescent material with a fluorescent material which emits yellow light such as a YAG fluorescent material, and a light emitting element which emits blue light, enables a light emitting device to emit white light with a warm tone by mixing light in the yellow to red light region with the blue light. The light emitting device emitting mixed light in the white region can increase the special color rendering index R9 close to 40 at the color temperature of about Tcp=4600 K.

[0134] Next, the production method of the fluorescent material according to the present invention ((Sr _X Ca _1−X ) ₂ Si ₅ N ₆ :Eu) will be described. The production method is not limited to the method that is described. The fluorescent material described above includes Mn and O.

[0135] The raw materials of Sr and Ca are ground. It is preferable to use elemental Sr and Ca for the raw materials, however, a compound such as an imide or an amide can be used. Also, B, Al, Cu, Mn, Al ₂ O ₃ , or the like, can be included in the raw materials of Sr and Ca. The raw materials of Sr and Ca are ground in a glove box in an argon atmosphere. The average particle diameter is preferably from about 0.1 μm to 15 μm, however, it is not limited to this range. The purity of Sr and Ca is preferably 2N and above, however, it is not limited to this grade. In order to improve the mixed state, a raw material can be used which is prepared by making an alloy of at least one of metallic Ca, metallic Sr, and metallic Eu, and then forming a nitride compound and grinding the formed nitride compound.

[0136] The Si raw material is ground. It is preferable to use elemental Si, however, a nitride, an imide, an amide, or the like, can also be used. For example, Si ₃ N ₄ , Si(NH ₂ ) ₂ , Mg ₂ Si or the like, can be used. The purity of Si is preferably 3N and above, however, a compound such as Al ₂ O ₃ , Mg, metallic borate (Co ₃ B, Ni ₃ B, CrB), manganese oxide, H ₃ BO ₃ , B ₂ O ₃ , Cu ₂ O, CuO, or the like, can also be included. Si is also ground in an argon or nitrogen atmosphere, in a glove box. This is the same procedure for the raw materials of Sr and Ca. The average particle diameter of the Si compound is preferably from about 0.1 μm to 15 μm.

[0137] Next, nitride compounds of Sr and Ca can be formed in a nitrogen atmosphere. The reaction formulas are shown by the following formulas, respectively.

3Sr+N ₂ Sr ₃ N ₂ (formula 1)

3Ca+N ₂ Ca ₃ N ₂ (formula 2)

[0138] Forming a nitride of Sr and Ca is carried out in a nitrogen atmosphere at from 600° C. to 900° C. for about 5 hours. Nitrides of Sr and Ca can be formed either as a mixture or individually. The nitrides of Sr and Ca are preferably of a high purity, however, a commercially available material can also be used.

[0139] Next, forming a nitride of Si raw material is carried out in a nitrogen atmosphere. The reaction formula is shown below in formula 3.

3Si+N ₂ Si ₃ N ₄ (formula 3)

[0140] A nitride of Si can be made in a nitrogen atmosphere at 800° C. to 1200° C. for about 5 hours. The silicon nitride used in the present invention is preferably of a high purity, however, a commercially available material can also be used.

[0141] Grinding is carried out on the nitride of Sr, Ca, or Sr—Ca. Sr, Ca, or a nitride of Sr—Ca is ground in an argon or nitrogen atmosphere in a glove box.

[0142] Similarly, grinding is carried out for the nitride of Si. Also, an Eu compound, Eu ₂ O ₃ is ground as well. As for an Eu compound, europium oxide is used, however, metallic europium, nitride europium, or the like, can also be used. It is preferable to use europium oxide having a high purity, however, a commercially available grade can also be used. After grinding, the average diameter of the nitride of the alkaline-earth metal, silicon nitride and europium oxide is preferably from about 0.1 μm to 15 μm.

[0143] The raw materials described above can include at least one element selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, O, and Ni. Also, the above elements, such as Mg, Zn, and B, may be mixed in the mixing process described below, in a predetermined compounding ratio. The elements described above can also be added to the raw materials individually, however, they are usually added as a compound. Compounds of this kind include H ₃ BO ₃ , Cu ₂ O ₃ , MgCl ₂ , MgO.CaO, Al ₂ O ₃ , metallic boride (CrB, Mg ₃ B ₂ , AlB ₂ , MnB), B ₂ O ₃ , Cu ₂ O, CuO, or the like.

[0144] After grinding, Sr, Ca, a nitride of Sr—Ca, silicon nitride, Eu ₂ O ₃ as a compound of Eu are mixed, and Mn is added. Because the mixture of these materials is susceptible to oxidation, the mixing process is carried out an argon or nitrogen atmosphere, in a glove box.

[0145] Finally, the mixture of Sr, Ca, a nitride of Sr—Ca, silicon nitride, Eu ₂ O ₃ as a compound of Eu is fired in a nitrogen atmosphere. By firing with additional Mn, a fluorescent material represented by the general formula (Sr _X Ca _1−X ) ₂ Si ₅ N ₈ :Eu can be obtained. The composition of the objective fluorescent material can be changed by changing the compounding ratio (mixing ratio) of each rare earth material.

[0146] A tubular furnace, a compact furnace, a high-frequency furnace, a metal furnace, or the like, can be used for firing. The firing can be carried out in the temperature range of from 1200° C. to 1700° C, however, the range from 1400° C. to 1700° C. is more preferable.

[0147] As for firing, a one step firing method in which the furnace temperature is gradually increased, and the firing is carried out at 1200° C. to 1500° C. for several hours, is preferable. However, a two step firing method (the multistage firing) wherein the first firing step is carried out at 800° C. to 1000° C., and the furnace temperature is gradually increased, and the second firing step is carried out at 1200° C. to 1500° C., can also be employed. The raw material of the fluorescent material is preferably fired using a crucible or a boat made of boron nitride (BN). Other than a crucible of boron nitride material, an alumina (Al ₂ O ₃ ) crucible can also be used.

[0148] Using the above production process, the desired fluorescent material can be obtained.

[0149] In addition, the fluorescent material that is capable of emitting a reddish light and that is usable in the present embodiment is not particularly limited and can include, for example, Y ₂ O ₂ S:Eu, La ₂ O ₂ S:Eu, CaS:Eu, SrS:Eu, ZnS:Mn, ZnCdS:Ag, Al, ZnCdS:Cu,Al, or the like.

[0150] The phosphors capable of emitting a reddish light are typified by aluminum garnet phosphors and nitride phosphors, produced as described above. These phosphors can be included in the single phosphor layer where more than two kinds of phosphors are included, or they can be included in the two layers of phosphor where each layer includes one or more than one kind of phosphor, formed around the light emitting element. The phosphor layer is formed by means of potting or stencil plate printing using an inorganic translucent member, such as a translucent resin or glass as adhesives.

[0151] Also, it is possible to use a method where the phosphor layer is formed after fixing the semiconductor light emitting element to the support member. It is also possible to use a method where the phosphor layer is formed on the semiconductor wafer, and is subsequently cut into chips. It is also possible to use a combination of both of these methods. According to such a configuration, a mixed light made up of light emitted from different kinds of phosphors can be obtained. In order to improve the mixing of light emitted from each fluorescent material and to decrease unevenness of the light, it is preferable that each kind of phosphor has a similar average diameter and shape. Also, it is preferable to arrange the nitride phosphor so it is placed closer to the light emitting element than the YAG phosphor. This is done because of consideration of the nitride phosphor absorbing a portion of light that is a converted wavelength from the YAG phosphor. According to such a configuration, absorption of a portion of the wavelength-converted light of the YAG phosphor by the nitride phosphor can be eliminated. Thus, the color rendering property of the mixed light can be improved compared to the case in which a mixture of a YAG phosphor and a nitride phosphor is included.

[0152] Alkaline Earth Metal Halogen Apatite Fluorescent Material An alkaline earth metal halogen apatite fluorescent material activated with Eu, including at least one element represented by M and selected from Mg, Ca, Ba, Sr, and Zn, and at least one element represented by M′ and selected from Mn, Fe, Cr, and Sn, can also be used. This composition enables the production of a light emitting device capable of emitting white light of a high luminance with good mass productivity. Especially, an alkaline earth metal halogen apatite fluorescent material activated with Eu and including at least one of Mn and Cl, has excellent light properties and weatherability. In addition, the fluorescent material can efficiently absorb light in the emission spectrum emitted from the nitride semiconductor. Furthermore, the fluorescent material is capable of emitting a white light, and can adjust the region of the white light range according to its composition. Additionally, the fluorescent material absorbs the ultraviolet rays and emits a yellow or red light having a high intensity. In addition, an example of an alkaline earth metal halogen apatite fluorescent material such as an alkaline earth metal chlorapatite fluorescent material can be included.

[0153] In the case of an alkaline earth metal halogen apatite fluorescent material represented by the general formula (M _1−x−y Eu _x M′ _y ) ₁₀ (PO ₄ ) ₆ Q ₂ (wherein M is at least one element selected from Mg, Ca, Ba, Sr, and Zn, M′ is at least one element selected from Mn, Fe, Cr, and Sn, Q is at least one element selected from F, Cl, Br, and I, 0.0001≦x≦0.5, 0.001≦y≦0.5) or the like, the light emitting device is capable of emitting mixed light and can be obtained with a good mass production efficiency.

[0154] Furthermore, in addition to the alkaline earth metal halogen apatite fluorescent material, in the case when at least one kind of fluorescent material selected from BaMg ₂ Al ₁₆ O ₂₇ :Eu, (Sr,Ca,Ba) ₅ (PO ₄ ) ₃ Cl:Eu, SrAl ₂ O ₄ :Eu, ZnS:Cu, Zn ₂ GeO ₄ :Mn, BaMg ₂ Al ₁₆ O ₂₇ :Eu,Mn, Zn ₂ GeO ₄ :Mn, Y ₂ O ₂ S:Eu, La ₂ O ₂ S:Eu, and Gd ₂ O ₂ S:Eu is included, a subtle adjustment of light color tone becomes possible. Further, a white light with an excellent color rendering property can be achieved with a relatively easy configuration. In addition, the fluorescent material can include Tb, Cu, Ag, Au, Cr, Nd, Dy, Co, Ni, Ti and Pr, or the like, in addition to Eu.

[0155] Also, the particle diameter of the fluorescent material used in the present invention is preferably in the range of from 1 μm to 100 μm, and more preferably in the range of 15 μm to 30 μm. A fluorescent material having the particle diameter of less than 15 μm tends to form an aggregation, and is densely settled down in a liquid resin, thereby decreasing the transmission efficiency of the light.

[0156] In the present invention, such an obstruction of light by the fluorescent material is prevented by employing a fluorescent material that does not have this tendency and thereby this improves the output of the light emitting element. Furthermore, a fluorescent material having a particle diameter in the range of the present invention has excellent properties for light absorption and light conversion efficiency, and has a broad excitation wavelength. Thus, by including a fluorescent material with a large particle diameter having excellent optical properties, it is also possible to efficiently convert wavelengths near the peak wavelength of light emitted from the light emitting element.

[0157] Here, the particle size in the present invention indicates the value obtained from the mass base particle size distribution. The mass base particle size distribution is obtained by measuring the particle distribution by means of a laser diffraction scattering method. Specifically, when the ambient temperature is 25° C. and the moisture content is 70%, each material is dispersed in a hexametaphosphoric acid having a concentration of 30%. The particle size distribution is then measured with a laser diffraction scattering-type device (SALD-2000A, Shimadzu Corp.) in a particle size range from 0.03 μm to 700 μm. The median diameter in the present specification indicates the particle size at the cumulative size distribution value of 50% in the mass base particle size distribution. The median diameter of the fluorescent material used in the present invention is preferably from 15 μm to 50 μm. Also, it is preferable to include a fluorescent material having a median diameter with the abovementioned range with a high frequency rate, preferably from 20% to 50%. By using such a fluorescent material having a small degree of fluctuation in particle diameter as just described, lack of uniformity in the distribution of the light color can be prevented, and a light emitting device capable of emitting favorable color tones of light can be obtained.

[0158] Also, it is preferable for the fluorescent material to have a shape similar to that of a dispersing agent used in the present invention. The term similar shape as used in the present specification means the difference in the deviation from circular (deviation from circular=circumference of a circle having equal area to the projected area of a particle/peripheral length of projection of a particle) among the particles is less than 20%. The deviation from circular indicates the degree of approximation away from a perfect circle. Accordingly, the light diffused by a dispersing agent and the light emitted from the excited fluorescent material are mixed in an ideal state, thereby a more uniform emission can be achieved.

[0159] Process 5: Separation Into Each Light Emitting Device

[0160] Next, each connecting part of the lead frame to each electrode is cut to form separate individual light emitting devices. Furthermore, where the package 1 , such as is shown in FIG. 3A or FIG. 6 , is formed through the use of a hanger lead which supports the package at the previously formed side recess 9 of the package, the support of the lead frame is removed after forming. Using the hanger lead enables the forming process to be carried out on each pair of electrodes simultaneously, thus decreasing the number of steps to form the light emitting device and increasing productivity.

[0161] Process 6: Forming the Lead Electrode 2

[0162] Next, the positive and negative electrodes protruding from the end face of the package 1 are bent along the side face of the package so that the J-bend type contact terminals are formed. Here, the contact terminal of lead electrode 2 is a portion of the lead electrode in contact with the conductive pattern of the mounting base and this allows the electric connection.

[0163] In the case where the positive lead electrode and the negative electrode protrude from the end faces of the minor axis sides of the main surface of the package in the present embodiment, it is preferable to bend the protruding portion toward the back side of the package, opposite from the main surface (see for example, FIG. 1A ). This avoids a harmful effect on the emission side from the molding solder and the mounting of the light emitting device to the wiring base can be carried out. Also, a pair of positive and negative lead electrodes 2 are inserted so as to protrude from the end face of the long axis side of the main surface of the package 1 . By bending the protruding portion of the lead electrodes toward the faces perpendicular to the emission face (see for example, FIG. 4A ), the contact surface area of the connection terminals and the conductive pattern placed on the mounting base can be increased. This arrangement enables a secure electric connection and accuracy in mounting.

[0164] Also, by bending the protruding portion of the lead electrodes, the light emitting device can be prevented from being pushed up from a temporary mounting face at the time when the reflow process is carried out such that the light emitting device is temporarily mounted to the mounting base. When the connection terminal portions are formed by bending the lead frames in this way, it is preferable that the wall face of the molding member on the mounting face side and the exposed faces of the lead electrodes are arranged so as to be on approximately the same plane. According to this configuration, the light emitting device can be mounted stably on the mounting base member.

[0165] Also, the structure of the contact terminal portion is not limited to the J-bend type and it may be made to have other structures such as a gull-wing type.

[0166] In the present embodiment, the area around the side faces where the lead electrodes are exposed, are preferably formed with a tapered shape which is tapered with predetermined angles, as shown in FIG. 3 and FIG. 6 . Thus, by bending the lead electrodes 2 to such an extent to be close to the side faces because of the elasticity of the lead electrode 2 , the connection terminal portion can be easily formed with any desired angle that is designed for stable mounting of the light emitting device.

[0167] The light emitting device of the present embodiment can be produced according to the above described processes.

[0168] The light emitting device thus formed is placed on the mounting base with a predetermined spacing to establish the electric conduction. It is preferable that the base member for the wiring base have excellent thermal conductivity, and an aluminum-based substrate, a ceramic-based substrate, or the like. In addition, where the surface of a substrate has a low thermal conductivity, such as a glass epoxy substrate or a paper phenol substrate, it is preferable to provide for heat release, by using a thermal pad, a thermal via, or the like. Also, electric conduction can be established between the light emitting diode and the wiring base by means of a conductive member, such as a solder. It is preferable to use a silver paste when taking the thermal release into consideration.

[0169] Translucent Member

[0170] In the present invention, a configuration capable of accurately fitting in the light entrance portion of the translucent member such as a lens or an optical guide plate made of a rigid-type translucent resin or glass or the like, can be made on the emission side or the light receiving side of the light emitting device. Here, “the light entrance-emitting portion” in the present specification is formed in the translucent member which directs light in a desired direction from the semiconductor device or directs light to the semiconductor device, and is a portion wherein the light from the semiconductor device enters. In some cases, this portion is called the “light entrance portion”. It is also a portion where the light is emitted toward the semiconductor device (in some cases, it is called the “emission portion”).

[0171] The translucent member in the present embodiment is a member where the reflection and refraction of light is used for guiding the incident light introduced in the member emitted from the light emitting device, in a predetermined direction. The translucent member also releases the light introduced into the translucent member, while adding a predetermined intensity distribution to the light. Also, the translucent member in other embodiments is a member which condenses light from the outside of the photo acceptance device which enters the translucent member in the direction of the photodetector.

[0172] Especially in the present embodiment, the translucent member used in the light emitting device has portions which individually introduce the incident light emitted from the light emitting device. The inner wall of the portion introducing the light has at least a mounting face contiguous with the first main surface, and a second mounting face contiguous with the second main surface of the light emitting device of the present mode. In addition, the portion introducing the incident light can be configured to fit the notched portion 13 formed on the main surface of the light emitting device shown in FIG. 5 .

[0173] As described above, according to the present invention, a light source having desired optical properties can be produced with a good process yield, by having the molding member capable of producing substantially constant shapes at all times, and by providing a configuration on the surface of the molding member which enables positioning with other translucent members.

[0174] Planar Light Source

[0175] The light source comprising an optical guide plate and a light emitting device may be a planar light source. In this planar light source, light enters from the light introducing portion at the side face of the optical guide plate and is released from another side face.

[0176] The optical guide plate of the present embodiment is a tabular translucent member, which uses the reflection of light on the inner wall of the member to guide the light from the light emitting device in a predetermined direction and release the light from the predetermined face to the outside of the tabular translucent member. Particularly, the optical guide plate of the present embodiment is a tabular optical guide body having a light releasing face which can be used as a planar light source for a backlight in a liquid crystal display, or the like.

[0177] As for the material for the optical guide plate, it is preferable to have excellent light permeability and good molding properties. An organic member such as an acrylic resin, a polycarbonate resin, an amorphous polyolefin resin, polystyrene resin, or the like, or an inorganic member such as glass or the like, can be used. In addition, it is preferable that the surface of the optical light guide plate have a profile irregularity of not more than 25 μm (cf. Japanese Industrial Standard).

[0178] Such an optical guide plate is installed so as to arrange the mounted face so that it sets the light introducing portion opposite to the main surface of the light emitting device. As for the installing method of the optical guide plate, a method such as fastening with a screw, adhesive bonding, welding, or the like, which is capable of easily positioning and secure bonding, can be used. The particular method can be selected according to a desired specification or requirement.

[0179] In the present embodiment, the second main surface of the package and the end face of the optical guide plate can be fastened together by an adhesive. Also, a diffusion sheet can be provided above the planar light source of the present invention. Thus, the present invention can be used as a light source for a direct type back light which illuminates other members such as a diffusion sheet or the like. The selection of the diffusion sheet has a decisive influence on the thickness and performance of the optical guide plate. Therefore, selection and evaluation of the diffusion sheet is preferably carried out in each case, according to the desired specification and requirements.

[0180] In the present embodiment, a diffusion sheet of about 100 μm in thickness, haze value of from 88% to 90% is used for a polycarbonate optical guide plate of 20 mm in thickness with excellent thermal resistance. Thus, unevenness of the light distribution between each of the light sources can be reduced and a uniform emission can be achieved. Such a diffusion sheet can be loaded on the optical guide plate directly or by means of welding. Also, when a cover lens is placed above the light source, the diffusion sheet can be fixed by placing it between the cover lens and the optical guide plate. The distance between the diffusion sheet and the optical guide plate is preferably from 0 mm to 10 mm. PET is most commonly used as the material for the diffusion sheet. However, the diffusion sheet is not limited to this material except that it should have a resistance against deforming or deteriorating due to heat generated by the light emitting diode.

[0181] The planar type light source thus obtained is capable of emitting light which is uniform and high in luminance over the entire area.

EXAMPLES

[0182] The following examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof.

Example 1

[0183] A surface mounting type of light emitting device is shown in FIGS. 1A and 1B . The light emitting element 4 is a nitride semiconductor element having an active layer